Common genetic factors may be behind both alcoholism and specific symptoms of eating disorders — particularly the binge eating and purging habits of bulimia nervosa, according to new research.
“Prior studies have shown that among people who had eating disorders, there were higher rates of alcohol abuse and dependence than those who didn’t have these eating disorders,” study author Melissa Munn-Chernoff, Ph.D., of Washington University School of Medicine in St. Louis, said.
“Also, studies had found higher rates of alcohol dependence in bulimia nervosa than anorexia nervosa.”
Earlier studies have shown a connection between the two disorders, but it was never clear whether genetics were the reason behind it.
To gain a better understanding of the underlying link, Munn-Chernoff and her team analyzed data from nearly 6,000 adult Australian twins—both identical and fraternal.
Identical twins share all of the same genes, while fraternal twins only share about half, making them genetically similar to siblings who aren’t twins. Studying both types of twins helped the researchers figure out whether conditions are more a product of genes or of the environment.
“Doing these types of studies is a necessary first step, because if they don’t show the traits are heritable, then we wouldn’t need to study the genes directly,” Munn-Chernoff said. “If identical twins are more similar to these behaviors than the fraternal twins, this would suggest that genes would be more important than environment.”
After conducting a series of interviews to determine the participants’ alcohol and eating habits, the researchers found that nearly 25 percent of men and 6 percent of women studied had been alcohol dependent at some point in their lives, and 11 percent of men and 13 percent of women had experienced problems with binge eating.
Additionally, 14 percent of women admitted to using two or more purging tactics. Men were not asked about their purging histories.
Once the researchers compared the twins to one another, they found that genetics play a vital role in the development of any of the three disorders, explaining 38 percent to 53 percent of a person’s risk. Furthermore, the same genetic risk factors for alcoholism seemed to make people vulnerable to binging and purging as well.
Although genetics play an important role in these disorders, Munn-Chernoff noted that a person’s environment still influences a person’s risk for alcoholism or bulimia.
“These types of studies capture the nature and nurture debate,” she said. “It’s always a combination of both, but these studies are designed to tap into that, and even though we didn’t find significant environmental risk factors, it doesn’t mean that they’re not important.”
Munn-Chernoff hopes the study will encourage physicians to associate alcoholism with bulimia. She said that if a patient presents the symptoms for one of these disorders, his or her doctor should look for symptoms of the other disorder.
“These two behaviors do occur together, not just in women but also in men,” Munn-Chernoff said.
“They could be linked for many different reasons. All forms of psychopathology share some kind of genetic component, and these two behaviors have not been looked at together as often as they should be.”
The study was published in the Journal of Studies on Alcohol and Drugs.